


Crossing Bridges

by Potrix



Category: Captain America (Movies), Iron Man (Movies), Marvel, Marvel Cinematic Universe, The Avengers (Marvel Movies)
Genre: Alternate Universe - Canon Divergence, Bucky Barnes & Steve Rogers Friendship, Clones, Developing Relationship, Domestic Fluff, Family, Fatherhood, First Dates, First Kiss, Fluff, Getting Together, Happy Ending, Hydra (Marvel), Kid Fic, M/M, POV Bucky Barnes, POV Tony Stark, Parent-Child Relationship, Parenthood, Pining, Post-Captain America: The Winter Soldier, Single Parents, Step-parents, cloning
Language: English
Status: Completed
Published: 2018-02-23
Updated: 2018-03-04
Packaged: 2019-03-22 18:15:50
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 8,011
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13769784
Author URL: https://archiveofourown.org/users/Potrix/pseuds/Potrix
Summary: “Thank you, really,” Barnes says, again, for at least the tenth time in the last two minutes. “Thank you, for doin’ this. I appreciate it.”With that, and a brief squeeze of Tony’s shoulder, Barnes is gone. Tony stares out into the empty hallway, blinking slowly, for several long moments after the elevator’s left his floor, before he manages to collect himself, and push the door closed with his elbow.Because his hands are full, holding Barnes’ sleeping son.





	1. Prologue: Tony

**Author's Note:**

> Originally written for a prompt over at [@imaginetonyandbucky](http://imaginetonyandbucky.tumblr.com): "Aftr TWS Bucky finds 5yo Hydra made w his DNA. For kids safety lets Steve find & move into Tower, but keeps to self. When Stv goes MIA Bky must go after him. He dsn't know Tony well, but hes been kind when workn on arm & Stv trusts him, so he thrusts his kid on a confused Tony (please details of Tony babysitting!). B&S home safe. Wk latr & Bky's kid keeps askn when they can do more science! w Tony & play w the bots again. Bky caves & asks bemused Tony. Playdates lead to real dates & happy family."
> 
> Naturally, as kid fics tend to do when I write them, it escalated. Oops? 
> 
> This is ~80% written, so updates should come pretty quickly (for once).

▪ we'll cross that bridge when we come to it ▪

“Thank you, really,” Barnes says, again, for at least the tenth time in the last two minutes. He hangs a tiny _Phineas and Ferb_ backpack on one of the hooks on the coat rack just inside Tony’s door, and deposits a bigger, plain black gym bag on the floor underneath it. “Everythin’ he needs is in the bag, his stuff for daycare’s in his backpack. Nat’s pickin’ me up in ten, one of us ‘s goin’ to contact you once we know more. Thank you, for doin’ this. I appreciate it.”

With that, and a brief squeeze of Tony’s shoulder, Barnes is gone. Tony stares out into the empty hallway, blinking slowly, for several long moments after the elevator’s left his floor, before he manages to collect himself, and push the door closed with his elbow.

Because his hands are full, holding Barnes’ sleeping son. Who Tony’s responsible for, now, for the foreseeable future. Even though he never actually agreed to it. He doesn’t think he said anything at all, actually, in the barely five minutes it had taken Barnes to bang on his door, storm into his apartment, explain the situation, and drop a small, vulnerable, breakable human in Tony’s arms.

“Oh, god,” Tony says, then stiffens when that makes the kid—Zachariah, Barnes had introduced him as Zachariah the one and only time Tony had seen him, when Barnes had moved them in two weeks ago—squirm, and frown in his sleep. Softening his voice, Tony murmurs, “Ssh, it’s okay, go back to sleep. Uh. Please?”

Zachariah makes a grumbly noise, and turns his face into Tony’s neck, but, thankfully, doesn’t wake up. He is getting heavy, though, so Tony, very carefully, walks over to the couch, and sits down gingerly. Zachariah stays asleep through it, and Tony breathes out a sigh of relief.

Right. Okay.

People who aren’t ready for parenthood have kids all the time, and not all of those kids take permanent emotional damage away from it. And Tony only needs to look after Zachariah for a couple of days, probably, hopefully; it’s not like he can screw the poor kid up in that amount of time. He’ll feed him, and do pretty much the opposite of everything Howard did, and they should be just fine until Barnes comes back home.

And if Tony keeps telling himself that, he might even start to believe it, eventually.

Not wanting to risk Zachariah waking up, Tony stays on the couch, happy to discover that there’s one of his StarkPads within reach. If he leans back a little, Zachariah can lie on his chest, and Tony even has his hands free. He brings up the details of Steve’s current mission, and settles in to read.

It’s when he’s going through Steve’s latest status update that Zachariah begins to stir. Tony holds his breath, even though he knows it’s a dumb thing to do—the kid’s hardly going to sleep through until Barnes comes home—but it’s no use. Zachariah lifts his head, looking around, bleary-eyed and confused.

“Daddy?” he asks, sounding incredibly small.

“Hey, buddy,” Tony says, and tries to smile reassuringly. He’s not sure how successful he is when Zachariah’s eyes widen, his small fingers tightening subconsciously in Tony’s shirt. “Do you remember me? I’m Tony, a—a friend of Barnes. Your dad.”

Zachariah doesn’t need to know that Tony and Barnes have exchanged maybe ten sentences since Barnes and Zachariah have moved in, almost exclusively all of them revolving around the logistics of the move, or about pending upgrades to Barnes’ prosthesis.

A little unsure, Zachariah nods. He sucks two of his fingers into his mouth, silently staring up at Tony.

Tony puts a tentative hand on top of Zachariah’s head, stroking it gently over his hair when Zachariah doesn’t pull away. “Your dad had to go, uh. Help. Your uncle Steve. With work. And he asked me to spend some time with you, while he’s gone. Does that sound okay?”

Zachariah bursts into tears.


	2. Chapter 1: Tony

For a few seconds, Tony is frozen still while Zachariah cries miserably. But then some instincts he hadn’t realised he even had kick in, and he wraps his arms around the distraught kid, holding him securely against his chest as he gets up, and starts pacing.

That’s what you do to calm down babies, he knows that much, and Zachariah’s—what? Four? Maybe five? Barely not a baby anymore, anyway. So Tony walks circles around his living area, stroking a hand up and down Zachariah’s back, and talking quietly.

He isn’t really sure what Zachariah might be interested in, just does what Jarvis used to do whenever Tony woke up with nightmares, and couldn’t go back to sleep; tells him about the Howlies. He can barely hear his voice over Zachariah’s wails, at first, but eventually, ever so slowly, Zachariah’s cries grow quieter, into occasional sniffles, and wet little hiccups.

When Tony’s finishing up the story about how Steve and Barnes got stuck in a tree in an Italian forest because of some angry boars, Zachariah’s smiling shyly, head resting against Tony’s shoulder. “You liked that, huh?” Tony asks, smiling back, and brushes some of the tears away from Zachariah’s flushed cheeks.

Zachariah nods, absently playing with the collar of Tony’s shirt. “Silly daddy,” he tuts through a yawn. Then, hopeful, he asks, “Bun Bun?”

That brings Tony up short. “Bun Bun?”

“I want Bun Bun,” Zachariah repeats, more insistent, before apparently remembering his manners, and adding, “Please?”

It takes Tony a moment, but then he remembers the bags out in the hall. Crouching with a little kid attached to his side turns out to be surprisingly difficult, never mind opening the gym bag, but Zachariah makes no move to let go of Tony, and Tony doesn’t want to risk upsetting him again. Barnes obviously knows his son’s priorities, though, because there, right on top, is a stuffed bunny.

Zachariah makes grabby hands at it the moment he spots it, and buries his face in its soft fur when Tony hands it over, mumbling contentedly. He’s obviously still tired—or exhausted from all the crying—and Tony considers trying to get him back to sleep, but it’s already close to half past eight. He probably shouldn’t let the kid sleep away the whole morning, at least not if he wants him to go to bed at a somewhat reasonable hour tonight.

Maybe they can both take a nap later. Tony’s certainly old enough that he appreciates every extra minute of sleep he can get, loath as he is to admit it.

He takes the bag and Zachariah’s backpack into one of the guest rooms, putting them on the bed for now, before heading to the kitchen. “How about breakfast? Are you hungry?”

“Yes,” Zachariah says, around the thumb in his mouth.

He looks reasonably calm now, though, so Tony leaves him to it. It’s probably not the best thing for his teeth, but the kid’s had one hell of a morning so far; he’s earned whatever comfort he or Tony can provide, Tony figures. And they’re going to be eating soon anyway.

“Okay,” Tony says, pulling open the fridge, and angling Zachariah so he can see what’s inside. “What’s it going to be, squirt?”

Zachariah considers his options, then points. “Bananas?”

“Good choice,” Tony agrees, pulling them out. “What else? Maybe some yoghurt?”

“No,” Zachariah says, wrinkling his nose. “Daddy makes pancakes on Sundays.”

Tony’s culinary skills are severely lacking, but pancakes he can do. Even if they never brown evenly, but he doubts Zachariah’s going to care too much. “With some chocolate chips? You like those?”

That makes Zachariah nod excitedly, and give Tony another small smile. It slips a little when Tony puts him on a chair at the table—he’s not going to handle a kid and a hot frying pan at the same time, even he knows that’s a disaster waiting to happen—so Tony quickly peels one of the bananas, and breaks off a piece for him. Then he goes and gets him a glass of juice, too, and one of his notebooks and some pens for good measure.

With Zachariah occupied for the moment, Tony makes a start on the pancakes. He’s got the batter ready quickly, and has the first batch in the pan when Zachariah asks, “Tony?”

“Yeah, kiddo,” Tony glances over his shoulder, “what’s up?”

“Are daddy an’ uncle Steve fighting bad guys?” Before Tony can come up with a child-friendly answer to that, Zachariah goes on with, “The bad guys who made me?”

Tony nearly drops his spatula. “Zachariah—”

“That’s only for when I’m being bad,” Zachariah says sternly. “When I’m being good you gotta call me Zach.”

“Zach,” Tony concedes. He turns down the heat on the stove, and turns around to face Zach, uselessly wiping his hands on his pants to buy himself some more time. He has no idea what, exactly, Barnes has told Zach about where he came from, but he must know the basics at least, if he’s aware that ‘the bad guys made him’, as he calls it. “Steve found a HYDRA base, yes, and your dad and Natasha went to help him take care of it.”

He’s so incredibly out of his depth, here, especially considering that Steve is MIA, and he has no idea what happened, what Barnes and Nat are walking into, and when—and in what condition—they’ll be back.

But Zach seems satisfied with that answer, at least for the moment. “That’s good,” he says, and picks up a pen, going back to whatever he was drawing before. “Daddy says they’re bad people, an’ he’s going to make them all go away so everyone’s safe.”

There’s no more heavy conversation while Tony finishes cooking, and then Zach’s too busy stuffing his face to talk at all. He has chocolate smeared around his mouth, and Tony would regret adding the whipped cream if Zach wasn’t looking so happy, grinning around his fork when Tony asks, “Good?”

Tony makes Zach carry his plate, glass, and cutlery over to the dishwasher once they’re done eating, then helps him put it all in there. “Good job,” he says when everything’s put away, and holds his hand out for a high-five. Zach slaps it, beaming, and then giggles when Tony pulls a face at his now sticky fingers. “Oh, you think that’s funny, do you?”

Zach shrieks when Tony picks him up, wiggling and laughing when Tony slings him over his shoulder to carry him to the bathroom. He insists on washing his hands on his own, but lets Tony clean his face with a washcloth, even though he grimaces through it, clearly not impressed.

After that, with Zach fed and mostly chocolate-free again, Tony’s at a bit of a loss as to what to do. It’s Sunday, meaning he has the day off unless there’s an Avengers or SI emergency, but he has no idea what Zach’s schedule is usually like.

The in-tower daycare for all employees is open, but Zach looks at him like he’s crazy when Tony asks if he’s supposed to be there. “Not when it’s the weekend.”

“Right.” Tony rubs a hand over the back of his neck, sheepish. “What do you normally do on weekends?”

“Play with daddy,” Zach says, leaning against Tony’s leg, looking up at him. “Or uncle Steve. Sometimes we go to the park, or do other stuff.”

Well. That’s not especially helpful. “Anything specific you want to do today?”

Humming, Zach considers that. Then his face lights up, and he tugs at Tony’s shirt, bouncing up and down on his toes. “Swimming! In the big pool!”

Which is how Tony finds himself in the swimming area on the recreational floor half an hour later, kneeling in front of Zach, who’s sitting on a deck chair, vibrating with excitement while Tony blows up his floaties. As soon as they’re secured to his arms he hops off the chair, and takes off towards the kiddie pool, whining when Tony says, “Hey, hey,” and snags him around the waist.

“Careful, no running,” Tony warns, waiting until Zach actually looks at him, pouting a little, before adding, “The floor’s slippery. I don’t want you to fall and hurt yourself, okay?”

“Okay,” Zach says impatiently, but he walks more slowly when Tony sets him back down.

Tony brings over the toys he’d found while looking for Zach’s swim shorts, sitting down on the edge of the shallow pool, feet in the water. Zach seems content to splash around, though, talking to himself as he fills and empties a small green bucket, over and over again. Tony has no idea what it is he’s playing, but he’s obviously having fun, which is the important thing.

Taking the opportunity while Zach’s doing his thing, Tony gets in some exercise of his own, swimming slow, unhurried laps, always keeping an eye on Zach to make sure he’s fine. He gets in maybe twenty minutes of swimming before Zach grows bored, toddling over to where Tony floats to the edge of the pool to meet him.

“Done already?”

“Wanna swim with you,” Zach mumbles, suddenly shy again. “In the big pool.”

Tony lets him jump in, even though the signs say not to, but it’s his pool, and there’s no one there to tell them not to. Zach is delighted, spluttering and grinning when he breaks the surface. He doggy paddles the few feet over to Tony, and wraps himself around Tony as best as he can, demanding Tony throw him.

They spend the better part of an hour in the pool, with Tony obligingly throwing Zach, and letting Zach chase him around, cackling madly whenever he manages to catch Tony. When Zach starts to flag, his head on Tony’s shoulder while Tony keeps them afloat, Tony decides it’s time to head back upstairs.

Zach fusses through his shower and getting dressed again, clearly tired, but perks up a little when Tony promises he can choose what they’ll have for lunch. Having learned from that morning, Tony talks Zach out of spaghetti and into penne with tomato sauce, which still make a mess, but, Tony tells himself, a smaller one than the spaghetti would’ve made.

After getting cleaned up yet again, Tony settles in on the loveseat in front of the TV, Zach in his lap, and nods seriously at Zach’s insistence that he doesn’t need a nap because he’s not sleepy at all. He says it while rubbing at his eyes and blinking slowly, and Tony has to bite back a smile.

He finds something suitable for a five-year-old, and pulls the blanket from the couch over them both, slowly rubbing Zach’s back. Zach is dead to the world five minutes into an episode of _SpongeBob_ , and Tony’s not far behind.

Kids are exhausting.


	3. Chapter 2: Tony

Zach is clingy and cranky after his nap, arms tight around Tony’s neck as he refuses to be put down. Tony tries, once, to set him down on the couch, but Zach ends up lying there dejectedly, sniffling quietly, hand curled limply around one of Bun Bun’s ears. It makes for a heartbreaking picture, and Tony lasts all of ten minutes before he goes to pick him up again.

With a whine, Zach buries his face in Tony’s neck, mumbling something too quiet for Tony to hear.

Tony cups the back of his head, bouncing him a little. “What’s that, buddy?”

“I miss daddy,” Zach whimpers, and starts crying.

It’s not like it was this morning, either; now, he’s crying quietly, barely making any noise at all, as if resigned to his fate. Somehow, it’s infinitely worse than the screaming and wailing.

Gently rocking Zach, Tony wonders if he’s ever really been away from Barnes like this. They were on the run for the first few of months after Barnes took Zach from that HYDRA facility, and then in hiding for a couple more before Barnes let Steve bring them both to the tower. Sure, Zach attends daycare to get him used to interacting with other kids, but that’s a few hours a day, and he knows Barnes will be right there to pick him up in the evening.

But now, Steve’s missing, and Barnes has gone after him, and no one knows when either of them will be back. The two most important people in Zach’s life are gone, and he’s been left with a virtual stranger who has no idea what he’s doing, and pretty much just makes this babysitting thing up as he goes.

Tony would be crying, too, if he were in Zach’s place.

“I know, kiddo, I’m sorry,” Tony says, and instinctively kisses the top of Zach’s head.

Then he pauses, unsure. But Zach doesn’t seem bothered by it, just snuggles in closely, absently running a finger over the Black Sabbath logo on Tony’s shirt. He also wipes his snotty face on Tony’s shoulder, which is kind of gross, but he’s slowly starting to calm down, so there’s that, at least.

“How about,” Tony suggests, and kisses Zach’s forehead, deliberately this time, because it seems to be working, “I show you some pictures of your dad’s new arm?”

Tony can’t do much to bring Barnes home, apart from providing the gear and tech—Iron Man and stealth ops go together about as well as pizza and pineapples—but maybe seeing Tony’s plans for his dad will cheer Zach up. Or make him miss Barnes even more, but Zach’s nodding and properly looking at Tony for the first time in half an hour, so Tony’s willing to take that chance.

Zach gasps when Tony carries him into the workshop, eyes big and round, glancing around curiously. Tony doubts he understands much of what he's telling him about the specs of the new prosthesis, but he smiles at the pictures Tony took of Barnes for reference. He flinches when he touches one of the holograms and it spins, but once Tony shows him how to ball it up and throw it in the holographic basketball hoop, Zach gleefully tosses empty notes all around the workshop, oohing and aahing when they burst or bounce upon hitting the walls and floor.

All the noise makes DUM-E come out of his loading station to see what’s going on. He whirrs at Zach, who stares up at him, mouth hanging open, before reaching out tentatively. When Tony nods at him, he touches one finger to DUM-E’s claw, then squeals when DUM-E lets out a series of beeps.

“He wants you to play,” Tony tells Zach, grabbing one of DUM-E’s balls to hand to Zach. “Here, go wild.”

Zach figures out quickly to throw or kick the ball for DUM-E to fetch, and happily chases after the ‘bot, and then the ball when DUM-E throws it for him, laughing the entire time.

“JARVIS,” Tony says, watching Zach hold onto DUM-E and let himself be dragged across the floor. “Keep everything locked up, make sure they don’t get into anything they shouldn’t.”

_“Heaven forbid someone do something dangerous in here.”_

Tony raises an eyebrow, mouth twitching tellingly, even as he says, “I don’t appreciate the sass, young man.”

_“My apologies, sir,”_ JARVIS says, not sounding sorry in the least. _“I shall do my best to keep young master Zach safe.”_

With Zach’s attention focused on DUM-E, Tony quickly checks if there’s been an update from Barnes or Nat, but there’s nothing after they checked in at Steve’s last known location. Sighing, Tony brings up some of the upgrades for the team on his to-do list, and gets to work.

He startles, some time later, when Zach drapes himself across his lap, grinning up at him. “Hi, squirt,” Tony says, smiling down at him, and ruffling his hair. “Did you have fun?”

“Yeah!” Zach chirps, bobbing his head. “What’re you doin’?”

“Trying to figure out what happened to Sam’s right wing.” Tony lifts Zach back into his lap, tucking him under his chin when Zach leans back against his chest. “Have you met Sam yet?”

Zach shakes his head. “Daddy talks to him on the phone sometimes,” he says. He tips his head back to look up at Tony conspiratorially. “He always uses lotsa bad words when he does.”

“I bet he does,” Tony agrees, amused. “Steve probably loves that.”

“Daddy says uncle Steve’s a hyp’crit, ‘cause he has the worst potty mouth out of everyone daddy knows.”

Tony can’t help but laugh at that. “That’s good to know,” he says, and it really is. He’ll have so much blackmail material by the time Nat, Steve, and Barnes get back. “Are you ready for dinner?”

Tony makes them mac and cheese out of the box, but he does add some broccoli and cauliflower. Zach purses his lips when he sees the veggies, picking them out and pushing them to the side of his plate. Then, when he’s done with the pasta, he drowns the veggies in ketchup, and eats them with an adorable scowl on his face.

Bedtime is surprisingly uneventful. Zach brushes his teeth while Tony supervises, gets on his PJs on his own, and seems okay to be put down in the guestroom, Bun Bun tucked in next to him. Tony reads him one of the books he finds in the bag, and Zach’s out like a light just three pages in.

With the kid hopefully out for the night, Tony spends the rest of the evening going through his schedule for the coming week. He finishes up a presentation, emails Pepper about an appointment with a potential investor, makes dinner plans with Rhodey, and then plays around with a few updates for the cleaning ‘bots’ code, just for fun.

By eleven, he’s yawning consistently, and has to admit that he’s only keeping himself awake to wait for word from Barnes or Nat. He forces himself to shut everything down, takes a quick shower, and quietly looks in on Zach before heading to bed himself.

It’s still dark out when he wakes up again, confused for a moment as to why, exactly, he is awake before he hears a quiet, shaky, “Tony?”

Rolling onto his side, Tony sees Zach standing next to the bed, clutching Bun Bun. He nervously shifts from foot to foot, not quite meeting Tony’s eyes. It’s not hard to guess what’s going on; Tony lifts the edge of his blanket, and, sure enough, Zach scrambles up onto the bed, right into Tony’s space.

He pillows his head on Tony’s chest, right over Tony’s heart. Tony puts a hand on his back, holding him close, and drifts off again.

The next morning is easier. JARVIS wakes them at seven to get ready for daycare, and Zach actually seems excited to go. They have muesli with fresh berries for breakfast, get dressed without trouble, and are out of the door by ten to eight, Zach wearing his backpack, and Tony carrying Zach in one arm, and his briefcase in the other.

Tony’s day is stressful, packed full of meetings, but he finds himself missing Zach anyway. Then he feels stupid, because he’s had Zach for one day, the majority of which he spent being sad about his dad. Feeling stupid doesn’t stop Tony from practically running out of the conference room after his last appointment of the day to go pick Zach up early, though.

Zach is ecstatic, and jumps on Tony as soon as he spots him, excitedly chattering about his day. He’s so busy relating a story about an apparently intense game of tag that he doesn’t notice they’re not going up to the penthouse until they step out of the elevator in Tony’s private garage.

When Tony asks him which car he thinks they should take, his eyes almost bug out of his head. Tony trails after him as Zach dashes from car to car, considering his option. He eventually stops next to the Hummer, pointing at it. “That one! It looks like a tank!”

Tony wisely doesn’t tell him that they have actual tanks—or something close to it, at least—at the new Avengers facility upstate, and goes to find a car seat instead. He curses internally the entire time he tries to get the seat into the car, and then Zach into the seat, while Zach laughs at the faces he makes.

Once they’re on the road, Zach asks, “Where are we goin’?”

He pouts and grumbles when Tony makes a big show of keeping it a secret, but his grumpy mood is instantly forgotten when Tony pulls into the McDonald’s parking lot. Tony grins to himself as he unbuckles a bouncy Zach, and keeps a firm hold of his hand as they walk inside and order.

It’s loud, full of screeching kids and yelling parents, and Tony sees several people try and fail to take sneaky looks at him, but Zach is smiling hugely around his chicken nuggets, happily kicking his feet under the table. He asks to go play in the ball pit when he’s done eating, and Tony congratulates himself on a job well done when he carries the sleepy kid back out to the car an hour later.

At home, he rouses Zach enough to make him brush his teeth and change out of his clothes, then puts him down in his own bedroom. Afterwards, he gets in another couple hours of work—still without updates on the Barnes front—before he joins Zach, who looks at him all groggy, and climbs up on Tony’s chest before dropping off again.

This time, Tony is woken by the sound of a camera. He blinks open his eyes, squinting at Steve standing in the doorway, phone held up, and grinning mischievously. Tony flips him off, which only makes Steve grin even wider.

“We’re back, mission’s done,” Steve whispers. “Buck’s hurt. Not badly, but he doesn’t want Zach to see him like that. I can take him, if you want?”

“Nah,” Tony rasps, shaking his head. “It’s fine, let him sleep. Bring breakfast tomorrow?”

Steve smiles. “‘Course. Coffee, too.”

Tony lifts his hand to give him a thumbs-up, and Steve laughs quietly on his way back out.


	4. Chapter 3: Bucky

“Daddy,” Zach whines, standing on his tiptoes so he can press his face against the oven door, “how much longer?”

“Fifteen minutes,” Bucky says patiently, biting back a smile. “Same as when you asked me twenty seconds ago.”

Zach huffs, put out, and Bucky feels almost bad telling him, “And then they’ll hafta cool for half an hour after that.”

The sound that Zach makes in response to that is one of pure frustration. He glares at Bucky, betrayed, as if Bucky is somehow personally responsible for the baking time of cheesecake brownies, and flops down right there on the floor, sprawling out dramatically.

From his place at the breakfast bar—ostensibly working on a report, but clearly watching the brownie disaster unfold instead—Steve chuckles. “Like father, like son.”

“Screw you, pal,” Bucky snarks back. Before either Steve or Zach can call him out on it, he pulls out a dollar, and stuffs it into the already overflowing swear jar. “There. Happy?”

“Thrilled,” Steve says, deadpan.

“Daddy,” Zach kicks at Bucky’s ankles until Bucky looks down at him, “how much longer?”

Bucky’s groan is, luckily, drowned out by Steve’s laughter. “Come on, little man,” Steve coaxes as he gets up, and swings Zach up into his arms. “Why don’t we go draw a picture for uncle Tony while we wait, huh? How’s that sound?”

Zach cheers and agrees enthusiastically, immediately all smiles again. Bucky just rolls his eyes, and sticks out his tongue when Steve smirks at him over his shoulder. He is thankful, though, because it gives him the time to finish cleaning up the kitchen, and change into a new shirt. Baking with a five-year-old always comes with casualties.

Steve comes back while Bucky’s assembling sandwiches for lunch, the brownies cooling on the counter, and snags a piece of bacon. “Zach’s putting the finishing touches on Tony’s drawing. And by that I mean glitter.”

“You’re the worst,” Bucky sighs, resigning himself to vacuuming the living room. Again. “It’s your apartment, too, I don’t know why you do this to yourself.”

“It’s cute, the puppy love thing he’s got going on,” Steve says, shrugging. But then his expression turns sly, and Bucky knows whatever’s about to come out of his mouth can’t be good before Steve says, “Even cuter than your little crush.”

Bucky throws the jar of mayo at his head, confident that Steve’s going to catch it. Or heal quickly, if not. “Stop talkin’ shit.”

“No, sure,” Steve says, all casual, and sets the jar back on the bar. “No crush. Setting a picture of a friend as your phone background is completely normal. As is staring at it with a dumb, lovesick look on your face.”

“It has my kid in it, too, jackass,” Bucky snaps, pressing the top slice of bread down on the sandwich a little harder than strictly necessary. “An’ you’re the one who took it.”

Steve raises his eyebrows. “To make fun of Tony for sleeping with his mouth open, yeah.”

“Whatever.” Bucky knows he’s blushing, but he can for damn sure pretend he’s not. “You’re a dick anyway.”

Zach skips into the kitchen right then, of course, covered in glitter and glue, and tells Bucky sternly, “You gotta put a dollar in the jar, daddy.”

Because he really is an ass, Steve doesn’t even try to hide his laughter. As punishment, Bucky plops Zach in his lap, messy as he is, for Steve to feed. Let someone else be sticky with condiments for once. Steve shoots him a knowing look, but dutifully cuts Zach’s sandwich into the requested triangles, and makes the appropriate noises during Zach’s retelling of his morning, even though Steve was there for most of it.

Bucky picks at his own food, absently pushing it around his plate more than actually eating it. Because the thing is, Steve isn’t wrong; Bucky is completely, embarrassingly gone on Tony. He’d noticed Tony was handsome and charming when he’d moved himself and Zach into the tower, of course, and then, later, while Tony’d worked on his arm, come to learn that Tony was incredibly kind and caring under all the distracting bluster of his public personality.

He’d acknowledged that Tony fit his type perfectly, and then immediately decided to ignore that knowledge. Bucky had only recently found back to and recovered himself, at that point, and then discovered Zach, and the fact that HYDRA had screwed him over in even more ways than he’d thought. Getting his dick wet had been pretty low on his list of priorities.

But then he’d had to go to Tony for help with Zach a couple of weeks ago, when Steve’d gone MIA. He’d been reluctant, initially, to trust someone he barely knew with Zach, but also out of other options. And then Tony had turned out to be amazing with Zach, and what’s Bucky supposed to do with that?

Zach hasn’t stopped talking about Tony since, and had thrown one hell of an epic tantrum once he’d realised that his sleepover with Tony had been supposed to be a one-time thing. So Bucky, sucker for his kid that he is, had sheepishly called Tony up to ask if Tony, maybe, would be up to spending an hour or so with Zach, just doing whatever. He’d expected Tony to agree, for Zach’s sake, but not that Tony would actually be excited about the suggestion.

He had been, though, and had taken Zach for an entire afternoon, much to Zach’s delight. After that, there’d been no stopping the inevitable. Zach had started insisting on seeing Tony every other day, Tony had proclaimed that a great idea, and Bucky’d had no reason to say no.

So, now, Tony picks Zach up early from daycare once a week to spend the afternoon ‘doing science’ with him, and then Bucky goes to pick Zach up from Tony’s place in the evening, staying over for dinner more often than not. When both Bucky and Steve are out on a HYDRA related mission that doesn’t require the other Avengers, Zach stays with Tony. And most Sundays, like today, Bucky, Zach, and sometimes Steve eventually end up in Tony’s apartment, bringing baked goods, and the mountains of drawings and crafts Zach’s made for Tony since last seeing him.

It’s not fair. Bucky never really stood a chance; Stark became Tony to him, Tony became uncle Tony to Zach, and Bucky fell. Pretty fucking hard.

“Daddy,” Zach says, and, from his tone of voice, not for the first time. Realising he finally has Bucky’s attention, he starts banging his hands on the bar. “I’m finished! Can we go see uncle Tony now?”

“Yeah, sure,” Bucky says, smiling weakly. “Go wash up, then we’ll go, ‘kay?”

Only Steve’s quick reflexes save Zach from tumbling off Steve’s lap, not that Zach seems to care. He just giggles when Steve catches him by the straps of his overalls, says, “Oopsie,” and dashes away the moment his feet hit the floor.

Once he’s gone, Steve nudges Bucky’s leg with his foot. “Hey. You should tell him. This entire situation’s making you miserable.”

Bucky gets up, collects their dishes, and moves over to the dishwasher to avoid Steve’s eyes. He’s well aware that he’s being obvious, he doesn’t need Steve to point it out to him. Hell, Tony probably knows all about it, too, and is just nice enough—nicer than Steve for sure—to not rub Bucky’s face in it. “Back off, Stevie.”

Steve joins him by the sink, wearing his Disapproving Face, capital letters implied, when Bucky glances over at him. “Buck, c’mon, I’m trying to—”

“Seriously, Steve, back the fuck off,” Bucky hisses harshly, slamming a glass down on the counter.

It shatters, and they both stare at it dumbly for a long moment. Then Steve sighs, and turns away to get some paper towels while Bucky loads the unbroken dishes into the dishwasher. They clean up in tense silence after that, which is only broken when Zach runs back into the room, attaching himself to Steve’s legs.

“Are you coming, too, uncle Steve?”

“Not today, bud,” Steve says, crouching down for a hug when Zach pouts at him. “Next time, okay?”

Zach huffs. “I guess.”

“Say bye to Steve, Zach, an’ go put on your shoes, please,” Bucky instructs, putting tin foil over the brownies. “Don’t forget your drawing.”

“Bye, uncle Steve,” Zach says, and smacks a wet, loud kiss to Steve’s cheek.

He squeals when Steve peppers kisses all over his face in return, and yells triumphantly once he gets free, but returns the, “Love you,” Steve calls after him.

“You too,” Steve tells Bucky. He straightens up again so he can sling an arm around Bucky’s neck, and kisses his cheek, too. “Even when you’re being an asshole.”

Bucky elbows him in the ribs. “Swear jar.”

Steve’s known Bucky for the better part of a century, though, and can read the gesture for what it is. He hugs Bucky properly for a moment, slaps him on the ass just to be a shit, and heads out with another, “Bye, buddy!” to Zach.

Tony’s already waiting for them when they step out of the elevator into the penthouse, and immediately picks Zach up to twirl him around. Zach laughs, thrilled, and Bucky’s heart squeezes.


	5. Chapter 4: Bucky

Bucky is half watching the ending of _Finding Nemo_ , half dozing against the arm of the couch when Tony murmurs a quiet, “Hey.”

He has Zach in his arms, fast asleep with his head on Tony’s shoulder, mouth slack around his thumb. Tony is swaying him gently as he smiles down at Bucky. “Is it okay if I put him down in his room up here? Or do you want to take him downstairs?”

“Go ‘head,” Bucky mumbles around a yawn, and lets his eyes flutter shut, listening to Tony’s footsteps disappear down the hall.

Zach’s room. Bucky hadn’t noticed, before, but he can’t actually remember the last time Tony called it a guest room. Not that it looks like one anymore; the furniture has been replaced to match the one in Zach’s room at Bucky’s, the hardwood’s gone in favour of a soft carpet, and a big part of Zach’s clothes and toys have migrated upstairs to Tony’s penthouse, too.

For all intents and purposes, Bucky and Tony are sharing custody. Which is great for Zach, who adores Tony, and for Tony, who’s just as taken with Zach, but not so much for Bucky, who’s already having a hard time getting over Tony.

Because down that road lies nothing but madness. Tony is so far out of Bucky’s league, he might as well be on a whole other plane of existence. All Bucky has to offer is a memory full of holes, so much red his ledger’s dripping with it, more trauma than a regular human should be able to survive, and a tiny clone he’s raising as his son.

Tony loving Zach doesn’t automatically translate to Tony loving Bucky. And Bucky better remember that, before he ends up hurting himself.

He opens his eyes again when the couch dips, rolling his head to look over at Tony. “Zach okay?”

“Didn’t even wake up when I put him in his PJs.” Tony stretches, cracking his neck, and Bucky very carefully does not look at the skin that’s bared where his shirt rides up. Much. Tony settles his arm along the back of the couch, and squeezes Bucky’s shoulder. “You could stay, too, you know?”

He’s smiling softly, and his thumb is absently brushing against Bucky’s throat, which is why he must notice how Bucky swallows hard, trying to not purposely misunderstand Tony’s offer. Eyes widening, Tony yanks his hand back, and ducks his head, which does nothing to hide the blush spreading across his cheeks.

“Not like that!” he squeaks, and, really. Any other time, Bucky’d be amused to see Tony so uncharacteristically flustered, but the fact that he’s about to be rejected kind of takes the joy out of it. “That’s not what I meant, shit. Sorry. This wasn’t—I had a plan for this, a good one, I promise. This isn’t how I wanted to do this.”

He rubs a hand over his head, grinning sheepishly at Bucky. But then he reaches out slowly, knuckles brushing over Bucky’s cheek before he cups Bucky’s face. “Tell me if I have this wrong?”

Bucky’s still frozen when Tony starts to lean in, but the moment their lips meet, Bucky surges into the contact, hands fisting into Tony’s shirt to pull him closer. Tony makes a surprised noise, but goes easily, pressing against Bucky with urgency. He nips at Bucky’s bottom lip, and Bucky opens up eagerly, moaning at the first touch of Tony’s tongue against his. Tony hums happily in response, one hand sneaking up under Bucky’s shirt, tracing over his abs, and—

“Tony,” Bucky says hoarsely, shuddering at the feeling of skin on skin, but manages to pull together enough brain power to still Tony’s exploring fingers, and put some distance between them. “Tony, what the fuck are you doin’?”

Tony’s breathing hard, pupils blown wide. “I thought,” he licks his lips, and slowly starts to frown, “we were on the same page?”

He sits back, rubbing at his eyes. “I thought you were waiting, because of Zach. Which, totally understandable, of course. And it’s not like spending time with the squirt was a hardship or anything, he’s a great kid. Amazing, really. But I got it wrong, didn’t I? You don’t want this at all, do you?”

Bucky is reeling. Tony sounds hurt, and, even worse, resigned because—because he thinks Bucky doesn’t want him back? But—he has to know, after how obvious Bucky’s been. He has to.

“You,” Bucky says, a little dumbly. “You’re interested? In me? Romantically?”

Tony just nods, expression hopeful, and sighs contentedly when Bucky moves back in to rest their foreheads together. “Tony,” he breathes, wrapping an arm around Tony’s waist, “I had no idea.”

“Yeah, I’m starting to get that,” Tony teases, eyes twinkling. “God, how didn’t you know? Steve’s been making fun of me for weeks.”

“Same,” Bucky snorts, and rolls his eyes. “He’s such an asshole.”

Tony laughs, open and happy, and Bucky can’t hold himself back any longer. He kisses Tony’s mouth, then his cheeks, his forehead, and the tip of his nose before moving back to his smiling lips. There he lingers, not deepening the kiss, just enjoying the feeling of it.

“Stay,” Tony murmurs against the corner of Bucky’s mouth, and swats at him when Bucky grins. “To sleep. But. Stay with me?”

“Can’t get rid of me now,” Bucky says—promises—and kisses him again.

*

Bucky wakes up alone, blanket tangled around him, but he can hear Tony putter around the kitchen, whistling to himself. Rolling over, Bucky buries his giddy smile in a pillow, happy to stay where he is for now.

It still seems surreal that Tony reciprocates his feelings, even after spending the night curled up in Tony’s bed. They’d decided to take their time with the physical part of their new relationship, for Zach’s sake as much as their own, and hadn’t done more than cuddle, and kiss some more. It had been perfect.

The door creaks open, then, followed by the sound of small, bare feet padding across the floor. Zach huffs a little as he pulls himself up onto the bed, but doesn’t hesitate to worm his way under the blanket, tucking himself into Bucky’s side, and skidding his icy fingers against Bucky’s ribs in the process.

Bucky grunts, giving himself away, and Zach immediately wiggles up so he’s lying on Bucky’s pillow, insistently poking at Bucky’s cheek. “Daddy. Daddy. Daddy.”

When he goes to pry open one of Bucky’s eyes, Bucky makes a grab for him, tugging him close. Zach squeals, kicking his legs as Bucky blows raspberries on his face, protesting, “No, daddy!”

“Shoulda thought about that before bein’ a little menace,” Bucky tells him, but does let up, allowing Zach to sprawl across his chest. “Sleep well?”

Zach nods, peering up at Bucky curiously. “Did you an’ uncle Tony have a sleepover?”

“Yeah, bud.” Bucky strokes a hand over Zach’s head, suddenly nervous. Zach is crazy about Tony, but that doesn’t mean he’ll be okay with his dad having a boyfriend. There’s nothing for it, though, so Bucky explains, “I like Tony a lot. A whole lot. So we’re probably gonna have sleepovers every once in a while.”

Whispering, as if he’s sharing a secret, Zach asks, “Did you kiss?” When Bucky says yes, Zach giggles, looking mischievous. “Uncle Steve said you have a crush on uncle Tony.”

One of these days, Bucky thinks darkly, he’s just not going to help out when Steve’s in trouble. Would serve him right.

From the doorway, holding a tray, and trying to look serious, Tony asks, “What about letting your dad sleep in until breakfast’s finished, huh?”

“He was awake already!” Zach protests, pouting up at Tony.

As Bucky watches, Tony’s face melts, going all soft and fond. Biting back a smile—of course Tony’s just as wrapped around Zach’s finger as Bucky himself is—Bucky sits up to take the tray from Tony, setting it down in the middle of the bed, while Tony picks up Zach, and settles back in with him in his lap.

Everything about this morning is new and different, and they’ll have to properly talk about it soon. For now, though, Bucky is content to sit here, sip his coffee, and listen to his son chatter about what he’s going to be doing at daycare today, head on Tony’s shoulder, and Tony’s hand on his knee, warm and safe.

**Notes for the Chapter:**

> Look at them, talking like adults. Can I get a hurray for honest communication? 
> 
> A short epilogue will be posted on Sunday. Hopefully. Fingers crossed.


	6. Epilogue: Bucky

There’s a soft knock on the door, and then, a moment later, it opens to reveal Steve. He’s holding Zach, who looks tired and grumpy, Bun Bun tucked between his face and Steve’s neck, even though he usually insists that seven and a quarter is too old to be seen in public with his favourite stuffed animal, or to be carried around. 

Bucky secretly lives for the few and far between moments when he’s sleepy enough to graciously allow Bucky to still pick him up. 

“Hey,” Steve whispers as he crosses the room, coming to perch on the edge of the hospital bed. “Everyone all right?”

Zach wiggles out of Steve’s hold, and crawls up the bed, flopping down on top of Bucky with one arm flung out to touch Tony’s side. Tony smiles down at him, and starts running the fingers of his free hand through his hair. 

“She hasn’t been up to seein’ us yet,” Bucky tells Steve, “but she’s fine, according to the doctors. Exhausted but fine. The baby, too.” 

As if on cue, the baby in question begins to fuss, little face scrunched up unhappily, and tiny hands curled into fists against Tony’s chest. Zach lifts his head to watch as Tony readjusts the baby, cooing softly, and gently rubbing its back.

“Hi,” Zach says, wide-eyed, “I’m Zach. I’m your big brother.” He reaches out, but hesitates before actually touching the baby, glancing up at Tony. “Papa, what’s the white stuff on his face?” 

“It’s called vernix,” Tony explains, thumb brushing the baby’s cheek. “It’s made up of cells, a little waxy, and it was protecting him while he was surrounded by amniotic fluid. It’ll wash off eventually, don’t worry.” 

“Gross,” Zach decides, but looks fascinated anyway. This time, he does touch the baby, stroking a very careful finger down its nose. The baby makes a little noise, and Zach beams proudly. “He likes me! Daddy, did you hear? He likes me!”

Unable to resist, Bucky pulls Zach closer, and smacks a kiss on his cheek. Zach squirms, but is still grinning, cuddling back against Bucky’s chest. “‘Course he likes you,” he says, chin resting on top of Zach’s head while Zach tries to make the baby grab his finger. “You’re his big brother.” 

“Does he have a name yet?” Steve asks, and laughs when Bucky groans. “Hey, as long as you agree on something before he starts kindergarten.”

“Haha,” Tony says, deadpan, nudging at Steve’s hip with his foot. He angles the baby a little better, so that Steve can see its face. “Meet your godson, Theodore Rupert Stark-Barnes. Theo.” 

Steve’s smile goes soft at that, and he nods eagerly when Tony asks him if he wants to hold Theo. They all feed him together for the first time when he gets hungry, and Bucky’s pretty sure Zach’s the only one staying calm through it. Steve leaves when it’s time for a diaper change, of course, as he always used to do whenever Bucky had to clean up one of his sisters or cousins. Zach decides that babies are disgusting, at that point, but wants to hold Theo anyway when Bucky brings him back to the bed. 

He makes Zach settle against a couple of pillows before placing Theo in his lap, on another pillow. When he meets Tony’s eyes over the top of Zach’s head, Tony is smiling, the small, fond thing that’s reserved solely for Bucky and Zach. And now Theo, too. 

“C’mere,” he murmurs, leaning in. Tony meets him halfway, sighing contentedly against Bucky’s lips. “Love you.”

“Love you, too,” Tony whispers back, and starts snickering when Zach complains, “Stop being gross.” 

“Hush, child,” Bucky says, and kisses Tony again, just because.

Zach huffs, long-suffering. “They’re always like that,” he tells Theo, very seriously. “But you’ll get used to it. And they’re pretty okay most of the time.”

Tony’s still laughing, burying his head in Bucky’s neck, and Bucky smiles, curling an arm around him. Yeah, they’re pretty fucking okay.

**Notes for the Chapter:**

> And that's it, folks.
> 
> Additional thoughts that were floating around my head while writing: 
> 
> \- Theo is totally named after Rhodey (Rupert). Zach’s middle name is Grant. 
> 
> \- Both Tony and Bucky know they don’t want Zach to stay an only child, even though they are unsure about how to go about that, initially. Bucky doesn’t want to use his DNA, because he has no idea what, exactly, HYDRA might have done to him, how they might have changed him, and he’s already afraid what that might mean for Zach.
> 
> \- Tony considers using a surrogate, but, eventually, decides that there are already enough kids out there/being carried right now that are looking for a home. So they start the adoption process.
> 
> \- They’re open to a child of any age, but prepare for a long wait anyway. They get lucky, though; during their second appointment at the adoption agency they meet a young couple in the waiting room. They’re both still in school, the pregnancy was unplanned, and they decided (after a lot of consideration and tears) to give the baby up for adoption once it’s born.
> 
> \- Tony immediately gets along with the couple because they’re both MIT students, too. Bucky’s pretty sure Tony’s ready to adopt them. Which doesn’t happen, obviously, but they do end up adopting their baby. 
> 
> \- They all agree on a half open adoption. The bio parents won’t get any updates or info about the baby/kid as it grows up, but if they (or the kid, who will be told about where he came from) ever decide they want to meet and get to know each other, Bucky and Tony will arrange it. 
> 
> \- Theo does eventually meet his bio parents. Tony and Bucky will always be his real parents, as far as he’s concerned, but his bio parents end up being like a cool aunt and uncle. When they eventually have kids they’re ready for, both Theo and Zach think of them as their little cousins.
> 
> THE END

**Author's Note:**

> There's a reblogable version of this [here](http://imaginetonyandbucky.tumblr.com/post/171095436886/aftr-tws-bucky-finds-5yo-hydra-made-w-his-dna-for) on tumblr. 
> 
> Go check out my other [work](http://archiveofourown.org/users/Potrix/works), or come over and say hi on [tumblr](http://potrix-the-queerschlaeger.tumblr.com).


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